1. Field of the Invention
The present invention relates to a projection zoom lens suitable for a projector for projecting an image formed on a film or slide or displayed by a liquid crystal display or the like on a screen in an enlarged image, and an optical projector provided with the projection zoom lens.
2. Description of the Related Art
An optical projector for projecting an image formed on a film or slide or displayed by a liquid crystal display or the like on a screen in an enlarged image has a projection optical system including a telecentric zoom lens. Most projection zoom lenses are four-group or five-group zoom lenses having variable-power ratios on the order of 1.2. In increasing the focal length and hence the magnification of most standard four-group or five-group telecentric zoom lenses, the first lens group at the front end of the zoom lens on the side of a screen, and the fourth or the fifth lens group at the rear end of the zoom lens on the side of an object point are fixed, and the lens groups between the first and the fourth lens group or between the first and the fifth lens group are shifted.
The conventional four-group or five group telecentric zoom lens, such as disclosed in JP2000-206409A, needs a large number of lenses to obtain a high aberration reducing characteristic and a wide field angle. Thus, the conventional projection zoom lens needs many lenses to reduce aberrations, such as distortion and coma, to a desired level, and hence the conventional projection zoom lens is complicated in construction and costly.